Module A-125 (VC Phaser) is a voltage controlled
phase shifter.
Phase shifting can be controlled either manually or by voltage control.
Other parameters which can be controlled are resonance (governing the depth of the comb
filtering, and tonal color) and mix (the amount of the original signal which is added to
the phase-shifted signal). The A-125 is used to generate the typical phaser
sound ("jet sound"). Due to the voltage control feature not only the
usual LFO-controlled phasings but even ADSR-, random-, sequencer- or
S&H-controlled phasings are possible. In combination with the Shepard
generator A-191 and several A-125 never ending barberpole
phasing effects come true.

For more detailed information please look at the
English user's manual A125_man.pdf

Below you will find the frequency
response of the A-125 for different phase shift settings.

In the first examples an LFO is used to
modulate the phase shift. At the beginning the original audio signal can
be heard (Mix control = CCW). Then the mix, after that the CV and then the
Resonance control is turned up.